Is it possible to add holes on volumetric clouds in eevee 2.92?
This is not volumetric and this is not exactly the same effect (I'll edit if I find something closer to what you show) but you could do something like that:

I've created a bezier circle and a cylinder, given the cylinder an Array modifier (with Fit Type &gt; Fit Curve with the curve as Curve) + Curve modifier (with a bezier circle as Curve Object) + Subdivision modifier + Displace modifier (with a Cloud texture):

Then I've given 2 or more shapekeys to the cylinder, stretched it so that it deforms, and keyframed the shapekeys: